Messages in this thread | | | Date | Wed, 10 Apr 2024 09:10:51 +0200 | Subject | Re: [PATCH v2 0/4] Speed up boot with faster linear map creation | From | David Hildenbrand <> |
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On 10.04.24 08:47, Itaru Kitayama wrote: > > >> On Apr 10, 2024, at 8:30, Itaru Kitayama <itaru.kitayama@linux.dev> wrote: >> >> Hi David, >> >>> On Apr 9, 2024, at 23:45, David Hildenbrand <david@redhat.com> wrote: >>> >>> On 09.04.24 16:39, Ryan Roberts wrote: >>>> On 09/04/2024 15:29, David Hildenbrand wrote: >>>>> On 09.04.24 16:13, Ryan Roberts wrote: >>>>>> On 09/04/2024 12:51, David Hildenbrand wrote: >>>>>>> On 09.04.24 13:29, David Hildenbrand wrote: >>>>>>>> On 09.04.24 13:22, David Hildenbrand wrote: >>>>>>>>> On 09.04.24 12:13, Itaru Kitayama wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>> On Apr 9, 2024, at 19:04, Ryan Roberts <ryan.roberts@arm.com> wrote: >>>>>>>>>>> >>>>>>>>>>> On 09/04/2024 01:10, Itaru Kitayama wrote: >>>>>>>>>>>> Hi Ryan, >>>>>>>>>>>> >>>>>>>>>>>>> On Apr 8, 2024, at 16:30, Ryan Roberts <ryan.roberts@arm.com> wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> On 06/04/2024 11:31, Itaru Kitayama wrote: >>>>>>>>>>>>>> Hi Ryan, >>>>>>>>>>>>>> >>>>>>>>>>>>>> On Sat, Apr 06, 2024 at 09:32:34AM +0100, Ryan Roberts wrote: >>>>>>>>>>>>>>> Hi Itaru, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> On 05/04/2024 08:39, Itaru Kitayama wrote: >>>>>>>>>>>>>>>> On Thu, Apr 04, 2024 at 03:33:04PM +0100, Ryan Roberts wrote: >>>>>>>>>>>>>>>>> Hi All, >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> It turns out that creating the linear map can take a significant >>>>>>>>>>>>>>>>> proportion of >>>>>>>>>>>>>>>>> the total boot time, especially when rodata=full. And most of the >>>>>>>>>>>>>>>>> time is spent >>>>>>>>>>>>>>>>> waiting on superfluous tlb invalidation and memory barriers. This >>>>>>>>>>>>>>>>> series reworks >>>>>>>>>>>>>>>>> the kernel pgtable generation code to significantly reduce the number >>>>>>>>>>>>>>>>> of those >>>>>>>>>>>>>>>>> TLBIs, ISBs and DSBs. See each patch for details. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> The below shows the execution time of map_mem() across a couple of >>>>>>>>>>>>>>>>> different >>>>>>>>>>>>>>>>> systems with different RAM configurations. We measure after applying >>>>>>>>>>>>>>>>> each patch >>>>>>>>>>>>>>>>> and show the improvement relative to base (v6.9-rc2): >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere >>>>>>>>>>>>>>>>> Altra >>>>>>>>>>>>>>>>> | VM, 16G | VM, 64G | VM, 256G | Metal, >>>>>>>>>>>>>>>>> 512G >>>>>>>>>>>>>>>>> ---------------|-------------|-------------|-------------|------------- >>>>>>>>>>>>>>>>> | ms (%) | ms (%) | ms (%) | >>>>>>>>>>>>>>>>> ms (%) >>>>>>>>>>>>>>>>> ---------------|-------------|-------------|-------------|------------- >>>>>>>>>>>>>>>>> base | 153 (0%) | 2227 (0%) | 8798 (0%) | 17442 >>>>>>>>>>>>>>>>> (0%) >>>>>>>>>>>>>>>>> no-cont-remap | 77 (-49%) | 431 (-81%) | 1727 (-80%) | 3796 >>>>>>>>>>>>>>>>> (-78%) >>>>>>>>>>>>>>>>> batch-barriers | 13 (-92%) | 162 (-93%) | 655 (-93%) | 1656 >>>>>>>>>>>>>>>>> (-91%) >>>>>>>>>>>>>>>>> no-alloc-remap | 11 (-93%) | 109 (-95%) | 449 (-95%) | 1257 >>>>>>>>>>>>>>>>> (-93%) >>>>>>>>>>>>>>>>> lazy-unmap | 6 (-96%) | 61 (-97%) | 257 (-97%) | 838 >>>>>>>>>>>>>>>>> (-95%) >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> This series applies on top of v6.9-rc2. All mm selftests pass. I've >>>>>>>>>>>>>>>>> compile and >>>>>>>>>>>>>>>>> boot tested various PAGE_SIZE and VA size configs. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> --- >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Changes since v1 [1] >>>>>>>>>>>>>>>>> ==================== >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> - Added Tested-by tags (thanks to Eric and Itaru) >>>>>>>>>>>>>>>>> - Renamed ___set_pte() -> __set_pte_nosync() (per Ard) >>>>>>>>>>>>>>>>> - Reordered patches (biggest impact & least controversial first) >>>>>>>>>>>>>>>>> - Reordered alloc/map/unmap functions in mmu.c to aid reader >>>>>>>>>>>>>>>>> - pte_clear() -> __pte_clear() in clear_fixmap_nosync() >>>>>>>>>>>>>>>>> - Reverted generic p4d_index() which caused x86 build error. >>>>>>>>>>>>>>>>> Replaced with >>>>>>>>>>>>>>>>> unconditional p4d_index() define under arm64. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> [1] >>>>>>>>>>>>>>>>> https://lore.kernel.org/linux-arm-kernel/20240326101448.3453626-1-ryan.roberts@arm.com/<https://lore.kernel.org/linux-arm-kernel/20240326101448.3453626-1-ryan.roberts@arm.com/> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>>>>> Ryan >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Ryan Roberts (4): >>>>>>>>>>>>>>>>> arm64: mm: Don't remap pgtables per-cont(pte|pmd) block >>>>>>>>>>>>>>>>> arm64: mm: Batch dsb and isb when populating pgtables >>>>>>>>>>>>>>>>> arm64: mm: Don't remap pgtables for allocate vs populate >>>>>>>>>>>>>>>>> arm64: mm: Lazily clear pte table mappings from fixmap >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> arch/arm64/include/asm/fixmap.h | 5 +- >>>>>>>>>>>>>>>>> arch/arm64/include/asm/mmu.h | 8 + >>>>>>>>>>>>>>>>> arch/arm64/include/asm/pgtable.h | 13 +- >>>>>>>>>>>>>>>>> arch/arm64/kernel/cpufeature.c | 10 +- >>>>>>>>>>>>>>>>> arch/arm64/mm/fixmap.c | 11 + >>>>>>>>>>>>>>>>> arch/arm64/mm/mmu.c | 377 +++++++++++++++++++++++-------- >>>>>>>>>>>>>>>>> 6 files changed, 319 insertions(+), 105 deletions(-) >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>> 2.25.1 >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> I've build and boot tested the v2 on FVP, base is taken from your >>>>>>>>>>>>>>>> linux-rr repo. Running run_vmtests.sh on v2 left some gup longterm not >>>>>>>>>>>>>>>> oks, would you take a look at it? The mm ksefltests used is from your >>>>>>>>>>>>>>>> linux-rr repo too. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Thanks for taking a look at this. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> I can't reproduce your issue unfortunately; steps as follows on Apple >>>>>>>>>>>>>>> M2 VM: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Config: arm64 defconfig + the following: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> # Squashfs for snaps, xfs for large file folios. >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_LZ4 >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_LZO >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_XZ >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_SQUASHFS_ZSTD >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_XFS_FS >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> # For general mm debug. >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_MAPLE_TREE >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_RB >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_PGFLAGS >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_DEBUG_VM_PGTABLE >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_PAGE_TABLE_CHECK >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> # For mm selftests. >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_USERFAULTFD >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_TEST_VMALLOC >>>>>>>>>>>>>>> ./scripts/config --enable CONFIG_GUP_TEST >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Running on VM with 12G memory, split across 2 (emulated) NUMA nodes >>>>>>>>>>>>>>> (needed by >>>>>>>>>>>>>>> some mm selftests), with kernel command line to reserve hugetlbs and >>>>>>>>>>>>>>> other >>>>>>>>>>>>>>> features required by some mm selftests: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> " >>>>>>>>>>>>>>> transparent_hugepage=madvise earlycon root=/dev/vda2 secretmem.enable >>>>>>>>>>>>>>> hugepagesz=1G hugepages=0:2,1:2 hugepagesz=32M hugepages=0:2,1:2 >>>>>>>>>>>>>>> default_hugepagesz=2M hugepages=0:64,1:64 hugepagesz=64K >>>>>>>>>>>>>>> hugepages=0:2,1:2 >>>>>>>>>>>>>>> " >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Ubuntu userspace running off XFS rootfs. Build and run mm selftests >>>>>>>>>>>>>>> from same >>>>>>>>>>>>>>> git tree. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Although I don't think any of this config should make a difference to >>>>>>>>>>>>>>> gup_longterm. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Looks like your errors are all "ftruncate() failed". I've seen this >>>>>>>>>>>>>>> problem on >>>>>>>>>>>>>>> our CI system. There it is due to running the tests from NFS file >>>>>>>>>>>>>>> system. What >>>>>>>>>>>>>>> filesystem are you using? Perhaps you are sharing into the FVP using >>>>>>>>>>>>>>> 9p? That >>>>>>>>>>>>>>> might also be problematic. >>>>>>>>>>>>>> >>>>>>>>>>>>>> That was it. This time I booted up the kernel including your series on >>>>>>>>>>>>>> QEMU on my M1 and executed the gup_longterm program without the ftruncate >>>>>>>>>>>>>> failures. When testing your kernel on FVP, I was executing the script >>>>>>>>>>>>>> from the FVP's host filesystem using 9p. >>>>>>>>>>>>> >>>>>>>>>>>>> I'm not sure exactly what the root cause is. Perhaps there isn't enough >>>>>>>>>>>>> space on >>>>>>>>>>>>> the disk? It might be worth enhancing the error log to provide the >>>>>>>>>>>>> errno in >>>>>>>>>>>>> tools/testing/selftests/mm/gup_longterm.c. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Attached is the strace’d gup_longterm executiong log on your >>>>>>>>>>>> pgtable-boot-speedup-v2 kernel. >>>>>>>>>>> >>>>>>>>>>> Sorry are you saying that it only fails with the pgtable-boot-speedup-v2 >>>>>>>>>>> patch >>>>>>>>>>> set applied? I thought we previously concluded that it was independent of >>>>>>>>>>> that? >>>>>>>>>>> I was under the impression that it was filesystem related and not something >>>>>>>>>>> that >>>>>>>>>>> I was planning to investigate. >>>>>>>>>> >>>>>>>>>> No, irrespective of the kernel, if using 9p on FVP the test program fails. >>>>>>>>>> It is indeed 9p filesystem related, as I switched to using NFS all the >>>>>>>>>> issues are gone. >>>>>>>>> >>>>>>>>> Did it never work on 9p? If so, we might have to SKIP that test. >>>>>>>>> >>>>>>>>> openat(AT_FDCWD, "gup_longterm.c_tmpfile_BLboOt", O_RDWR|O_CREAT|O_EXCL, >>>>>>>>> 0600) = 3 >>>>>>>>> unlinkat(AT_FDCWD, "gup_longterm.c_tmpfile_BLboOt", 0) = 0 >>>>>>>>> fstatfs(3, 0xffffe505a840) = -1 EOPNOTSUPP (Operation not >>>>>>>>> supported) >>>>>>>>> ftruncate(3, 4096) = -1 ENOENT (No such file or >>>>>>>>> directory) >>>>>>>> >>>>>>>> Note: I'm wondering if the unlinkat here is the problem that makes >>>>>>>> ftruncate() with 9p result in weird errors (e.g., the hypervisor >>>>>>>> unlinked the file and cannot reopen it for the fstatfs/ftruncate. ... >>>>>>>> which gives us weird errors here). >>>>>>>> >>>>>>>> Then, we should lookup the fs type in run_with_local_tmpfile() before >>>>>>>> the unlink() and simply skip the test if it is 9p. >>>>>>> >>>>>>> The unlink with 9p most certainly was a known issue in the past: >>>>>>> >>>>>>> https://gitlab.com/qemu-project/qemu/-/issues/103 >>>>>>> >>>>>>> Maybe it's still an issue with older hypervisors (QEMU?)? Or it was never >>>>>>> completely resolved? >>>>>> >>>>>> I believe Itaru is running on FVP (Fixed Virtual Platform - "fast model" - >>>>>> Arm's architecture emulator). So QEMU won't be involved here. The FVP emulates >>>>>> a 9p device, so perhaps the bug is in there. >>>>> >>>>> Very likely. >>>>> >>>>>> >>>>>> Note that I see lots of "fallocate() failed" failures in gup_longterm when >>>>>> running on our CI system. This is a completely different setup; Real HW with >>>>>> Linux running bare metal using an NFS rootfs. I'm not sure if this is related. >>>>>> Logs show it failing consistently for the "tmpfile" and "local tmpfile" test >>>>>> configs. I also see a couple of these fails in the cow tests. >>>>> >>>>> What is the fallocate() errno you are getting? strace log would help (to see if >>>>> statfs also fails already)! Likely a similar NFS issue. >>>> Unfortunately this is a system I don't have access to. I've requested some of >>>> this triage to be done, but its fairly low priority unfortunately. >>> >>> To work around these BUGs (?) elsewhere, we could simply skip the test if get_fs_type() is not able to detect the FS type. Likely that's an early indicator that the unlink() messed something up. >>> >>> ... doesn't feel right, though. >> >> I think it’s a good idea so that the mm kselftests results look reasonable.
Yeah, but this will hide BUGs elsewhere. I suspect that in Ryan's NFS setup is also a BUG lurking somewhere in the NFS implementation. But that's just a guess until we have more details.
>> Since you’re an expert on GUP-fast (or fast-GUP?), when you update the code, could you print out errno as well like the split_huge_page_test.c does
While we could, I don't see much value in that for selftests. strace log is of much more valuable to understand what is actually happening (e.g., fstatfs failing), and quite easy to obtain.
>> Thanks, >> Itaru. > > David, attached is the straced execution log of the gup_longterm kselftest over the NFS case. > I’m running the program on FVP, let me know if you need other logs or test results.
For your run, it all looks good:
openat(AT_FDCWD, "/tmp", O_RDWR|O_EXCL|O_TMPFILE, 0600) = 3 fcntl(3, F_GETFL) = 0x424002 (flags O_RDWR|O_LARGEFILE|O_TMPFILE) fstatfs(3, {f_type=TMPFS_MAGIC, f_bsize=4096, f_blocks=416015, f_bfree=415997, f_bavail=415997, f_files=416015, f_ffree=416009, f_fsid={val=[0x8e6b7ce6, 0xe1737440]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0 ftruncate(3, 4096) = 0 fallocate(3, 0, 0, 4096) = 0
-> TMPFS/SHMEM, works as expected
openat(AT_FDCWD, "gup_longterm.c_tmpfile_WMLTNf", O_RDWR|O_CREAT|O_EXCL, 0600) = 3 unlinkat(AT_FDCWD, "gup_longterm.c_tmpfile_WMLTNf", 0) = 0 fstatfs(3, {f_type=NFS_SUPER_MAGIC, f_bsize=1048576, f_blocks=112200, f_bfree=27954, f_bavail=23296, f_files=7307264, f_ffree=4724815, f_fsid={val=[0, 0]}, f_namelen=255, f_frsize=1048576, f_flags=ST_VALID|ST_RELATIME}) = 0 ftruncate(3, 4096) = 0 fallocate(3, 0, 0, 4096) = 0
-> NFS, works as expected
Note that you get all skips (not fails), because your kernel is not compiled with CONFIG_GUP_TEST.
ok 1 # SKIP gup_test not available
-- Cheers,
David / dhildenb
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